package com.changgou.system.util;

import io.jsonwebtoken.JwtBuilder;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;
import java.util.Date;

public class JwtUtil {
    //有效期为
    public static final Long JWT_TTL = 3600000L;//60*60*1000一小时
    //设置秘钥明文
    public static final String JWT_KEY = "itcast";

    /**
     * 创建token
     *
     * @param id
     * @param subject
     * @param ttlMillis
     * @return
     */
    public static String createJWT(String id, String subject, Long ttlMillis) {
        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
        long nowMillis = System.currentTimeMillis();
        Date now = new Date(nowMillis);
        if (ttlMillis == null) {
            ttlMillis = JwtUtil.JWT_TTL;
        }
        long expMillis = nowMillis + ttlMillis;
        Date expDate = new Date(expMillis);
        SecretKey secretKey = generalKey();

        JwtBuilder builder = Jwts.builder()
                .setId(id)//唯一id
                .setSubject(subject) //主题 可以是json数据
                .setIssuer("admin") //签发者
                .setIssuedAt(now) //签发时间
                .signWith(signatureAlgorithm, secretKey) //使用HS256 对称加密算法签名，第二个参数为秘钥
                .setExpiration(expDate); //设置过期时间
        return builder.compact();

    }

    /**
     * 生成加密后的秘钥secretKey
     *
     * @return
     */
    private static SecretKey generalKey() {
        byte[] encodeKey = Base64.getDecoder().decode(JwtUtil.JWT_KEY);
        SecretKey key = new SecretKeySpec(encodeKey, 0, encodeKey.length, "AES");
        return key;
    }


}
